1. Field of the Invention
The present invention relates to a ladder device, particularly to a ladder device for climbing up to and climbing down from a walkway mounted on a vehicle body of a construction machinery.
2. Background Information
In work vehicles such as large bulldozers and wheel loaders, a cab and a walkway serving as a communication path to the cab are disposed in a higher position. Further, a ladder device is mounted for climbing up to and climbing down from the cab through the walkway. Ladder devices, having been proposed so far, are of a stationary type fixed to a vehicle-side member and of a movable type configured to be moved between a boarding posture and a retracted posture. The movable type ladder device is configured to be disposed between the ground and the walkway in the boarding posture while deployed. On the other hand, the movable type ladder device is configured to be retracted to a lateral part of a vehicle body so as to be oriented in a substantially horizontal direction in the retracted posture.
For example, a movable type ladder device described in Australia Patent No. 713990 is provided with a first axis in the horizontal direction and a second axis perpendicular to the first axis. Further, the upper end portion of a ladder main body is supported rotatably about these axes. In this device, the ladder main body, set in the boarding posture, is firstly rotated about the first axis and is accordingly lifted upwards, and is then stopped in an upper position beyond the retracted posture. Next, the lifted ladder main body is rotated about the second axis and is accordingly pulled towards the vehicle body. Then, the ladder main body is further rotated about the first axis and is accordingly moved downwards. Thus, the ladder main body is set in the retracted posture.
On the other hand, a movable type ladder device described in U.S. Pat. No. 7,870,932 is provided with a single axis that the upper side thereof is forwardly slanted in a vehicle side view, and the upper part of the ladder main body is rotatably supported by the slanted axis. In this device, the ladder main body, set in the boarding posture, is rotated about the slanted axis, and is set in the retracted posture. In the retracted state, the ladder main body is disposed along the vehicle body in such a posture that the vehicle-body-side (back side) surface thereof is oriented outwards.